Circuit breaker



May 30, 1961 J. w. BULLOCK ET AL 2,986,620

CIRCUIT BREAKER Filed Dec. 29, 1959 4 Sheets-Sheet 1 rim/1v m BULLOCK P1255 ro/v D. Bow/Ml INVENTORS.

May 30, 1961 J. w. BULLOCK ETAL 2,986,620

CIRCUIT BREAKER Filed Dec. 29, 1959 4 Sheets-Sheet 2 g .96 J0 M 54 f6 12 9% 7 34 zfomv W BULLOCK 4 $7'0N D. owml 34 a 14 36 PEE uvfivmxs 40 BY 30 M /m/ y 1961 J. w. BULLOCK ET AL 2,986,620

CIRCUIT BREAKER Filed Dec. 29, 1959 4 Sheets-Sheet 4 i UK?) 170 I I Ga I 1;. Q

CIb/l/V 74 BULLOCK PE$TON D. Rowe/v INVENTORS.

BWQAM. WM

United States Patent CIRCUIT BREAKER John W. Bullock, Sherman Oaks, and Preston D. Rowan, Fullerton, Calif., assignors to Briles Products, Inc., El Segundo, Calif., a corporation of California Filed Dec. 29, 1959, Ser. No. 862,535

Claims. (Cl. 200-116) The present invention relates to circuit breakers for electrical systems, and it relates particularly to a novel circuit breaker which, although small and compact, and light in weight, is capable of meeting extreme service requirements such as those found in aircraft electrical systems.

It is an object of the present invention to provide a circuit breaker of the type that is trip free, that is, one which can not be manually re-set while a condition of current overload persists, which is simple in construction, having a minimum number of operative parts, and which may be made relatively small in size and light in weight, yet which has a long operative life, is capable of handling heavy current loads, and includes strong, positive spring means for separating the contacts upon release of the breaker by a current overload, while at the same time being safe against accidental release, even under extreme conditions of shock and vibration.

Another object of the present invention is to provide a circuit breaker of the character described which includes three principal units, a switch assembly, a latching assembly for moving the switch assembly to the make" or closed position and for holding the switch assembly in this position, and a thermoelement release assembly for releasing the latching assembly and permitting the switch assembly to return to the break or open position, all three of these principal portions of the breaker being compressed together in the make position, with the contacts of the switch assembly being held tightly in the engaged position against strong spring force which urges the contacts apart, this compression of the parts in the make position holding all movable parts of the breaker tight against shock and vibration, and providing an excellent electrical connection through the contacts.

Another object of this invention is to provide a circuit breaker of the character described in which the thermoelement is compressed between the contacts and the latching mechanism in the operative, make position of the breaker, so as to hold the contacts in the engaged position against the force of a contact separating spring, and so as to apply sufiicient force to the latching mechanism to frictionally hold the latching mechanism in its latched position against spring latch release means, thermal shift of the thermoelement resulting from a current overload causing the thermoelement to move off of a shoulder to relieve the holding pressure between the latching mechanism, the thermoelement and the contacts, whereby the latch will be released, permitting the contact separating spring to open the contacts.

It is a further object of the present invention to provide a circuit breaker of the character described which inbreaker of the character described wherein the thermoice element for releasing the breaker is provided in elongate, helical form, one end of the thermoelement being positioned closely adjacent to the contacts, and the other end being engageable against the latching assembly, the coiled thermoelement providing a substantial magnetic blow-out action to reduce arcing upon separation of the contacts.

Another object is to provide a circuit breaker of the character described wherein the contacts, coiled thermoelement and latching assembly are axially aligned within a small cylindrical housing, with the contacts disposed in one end of this housing, whereby further blow-out action results from the blast efiect of the suddenly expanding gases in the contact end of the housing.

Another object is to provide a circuit breaker of the character described wherein a shaft forming a part of the latching assembly extends axially into the coiled thermoelement, whereby eddy current repulsion or magnetic attraction resulting from the surge of current through the thermoelement will act upon this shaft to supplement the force of the latch release spring in returning the latch to the break position.

It is a further object of the present invention to provide a circuit breaker of the character described of the double break type having a pair of fixed contacts and a respective pair of movable contacts, wherein a shunt ring is interposed between the contact separating spring and the movable contacts, so as to divert a portion of the current passing through the breaker away from the thermoelement, the electrical resistance value of the shunt ring controlling the sensitivity of the breaker, whereby a standard circuit breaker unit may be provided, and may be adapted for different current and sensitivity requirements by merely providing shunt rings of different electrical resistance values.

It is also an object of this invention to provide a circuit breaker of the character described of the double break type, having a pair of fixed contacts and a pair of movable contacts, the movable contacts pivoting in a rocking action during the closing and opening thereof so as to produce a self-wiping action to keep the contacts clean.

Further objects and advantages of this invention will appear during the course of the following part of this specification wherein the details of construction and mode of operation of a preferred embodiment are described with reference to the accompanying drawings, in which:

Fig. l is an exploded view illustrating the various parts of a presently preferred embodiment of the invention employing a cylindrical casing.

Fig. 2 is a vertical, axial section, partly in elevation, illustrating the assembled device of Fig. 1 in the make" position.

Fig. 3 is a vertical, axial section, partly in elevation, similar to Fig. 2, but illustrating the breaker in the break position.

Fig. 4 is a vertical, axial section, with portions in elevation, taken on line 4-4 in Fig. 2.

Fig. 5 is a vertical, axial section, with portions in elevation, taken on the line 5-5 in Fig. 3.

Fig. 6 is a vertical, axial section, with portions in elevation, taken on line 6-6 of Fig. 5.

Fig. 7 is a sectional view taken on the line 7-7 in Fig. 2.

Fig. 8 is a sectional view taken on line 88 of Fig. 2.

Fig. 9 is a vertical, axial section, with portions in elevation, illustrating an alternative embodiment of the invention enclosed in a generally fiat, rectangular housing, and which includes ambient temperature compensating means, in the form of a temperature sensitive, expanding and contracting bellows.

Fig. 10 is a vertical, axial section, partially in eleva "messes tion, similar to Fig. 9, but illustrating another, preferred form of ambient temperature compensating means, which includes a bimetal thermoelement. p

Fig, l 1 a greatl y enlarged axial section illustrating th pre erre lateh'ing assembly employed in the embodirn ents shown in Figs.9 and 10. I

Fig. 12is a vertical section'taken on line 12-12 of FigulQ further illustrating the presently preferred ambient temperature adjusting means.

Eig. 13 is a horizontal section taken on line 13-13 of Fig. 10 also illustrating the preferred ambient temperature adjusting means.

Referring to the drawings, and at first particularly to jFig's. 1-8 thereof, the cylindrical embodiment 19 of the invention includes a cylindrical shell or casing 12 which may be composed of plastic or of a suitable metal such as aluminum. An end plug 14 composed of insulating 'material is threadedly engaged in the bottom of shell 12. The bottom end plug 14 is suitable for supporting the fixed contact members and their respective external conductbrs. A top 'end plug 16 is threaded-1y engaged the upper end of shell 12, and is adapted to support the latching assembly as hereinafter described.

A pairof fixed contact members 18 are mounted on bottom end plug 14 adjacent to the inner wall of the end plug, and a pair of conductors 20 are connected to the respective contact members 18 and extend through end plug14 so as to provide means for connecting the circuit breaker into an electrical circuit.

It is preferred toprovide the bottom end plug 14 with an axially directed, annular wall 22 spaced a short dis tance inside of the inner wall of the outer shell 12, with 1 a transverse web 24 dividing the region enclosed in wall 22 into two recesses in which the contacts 18 are respectively positioned. v I y A pair of 'movable contact members 26 are disposed in -spaced relationship to the respective fixed contact members 18, being integrally attached to respective contact support arms 28 which are pivotally mounted on a breaker bar 30 by means of spaced pivot pins 32. Breaker bar '30 is provided at it sides with a pair of axially extending ears 34 which are slidably mounted in respective axial grooves 36 in the-inner wall of the cylindrical casing 12,

' whereby to permit axial sliding movement of the breaker bar 30 within casing 12.

Radially outwardly projecting fingers 38 are provided on the respective contact support arms 28, the fingers 38 p being engaged by shunt ring '40 which is forced against fingers 38 by means of contact separating coil spring 42. Spring '42 engages shunt ring 40 at one of its ends, the other end of spring 42 being disposed around the end plug wall 22 and seating against the end plug 14. Coil spring 42 is a relatively strong compression spring, and in the break or unactuated position of the circuit breaker as shown in Figs. 3, and 6, spring 42 holds the movable contact members 26 in spaced relation to the fixed contact members 18. It is to be noted that the coil compression spring 42 of relatively large diameter'for driving the contacts apart is much more positive in action and less likely to break than the conventional coiled tension springs having fragile end loops which are employed in circuit breakers. p

A bimetal thermoelement 44 of helical form is axially disposed in casing 12, and has its lower end attached to breaker bar 30 as by means of atransverse pin 46. The lower end of thermoelement 44 is electrically connected to one of the contact support arms 28 by means of a flexible conductor or pig tail 48, while the upper end of thermoelement 44 is electrically connected to the other contact support arm 28 by means of a second flexible conductor or,pig tail 50.

Bimetal thermoelement 44 is provided at its. upper end with an integral, radially outwardly directed thrust finger 52 adapted to be engaged. by the latching assembly in the manner hereinafter described.

The breaker bar 30 is composed of an insulating material, while the contact support arms 28 are metallic, conducting members. Thus, when the breaker is in its make or actuated position, current is conducted through the breaker from one of the external conductors 20 through its respective fixed contact member 18 and movable contact member 26, thence through the respective contact support arm 28, through one of the flexible conductors 48 and 50, thence through the length of the coiled thermoelement 44 and through the other flexible eonductor 48 or 50 to the other contact support arm 28, and thence through its respective movable contact member 26 and fixed contact member 18 to the other external conductor 20. This current which passes through the thermoelement in the actuated position of the device will, by heating the thermoelement, cause the thrust finger 52 forming a part of the thermoelement to mechanically shift through an arc, the extent of which depends upon the amount of current passing through the thermoelement. When a current overload condition is present, this are will be suflicient to release the latching assembly in the manner hereinafter described.

A portion of the current which passes through the circuit breaker will be by-passed from the thermoelement, this portion of the current passing directly from one ofthe contact support arms 28 to the other through shunt ring 40. It will thus be apparent that the sensitivi' ty of the unit may be varied by providing shunt rings 40. of different electrical resistance values, thus to permit more or less current to flow through the thermoelement 44. This permits the circuit breaker to be provided in one standard form for uses requiring various sensitivities, by merely varying the resistance value of the shunt ring in accordance with the sensitivity desired. It is to be noted that the positioning of the contacts in the bottom end of the casing causes the suddenly expanding gases which result from arcing upon breaking of the contacts to be directed axially away from the contacts, to provide a strong gas blow-out action so as to shorten the time duration of arcing. Arcing is further reduced by employing the coiled thermoelement 44 with its lower end proximate the contacts, surge currents through the thermoelemeut upon breaking of the conlease member 54 is slidable within an axial bore in the upper end plug 16, end plug 16 having a flange 62 thereon which extends radially inwardly of the bore 60 so as to provide a latching shoulder 64 against which the latch member is frctionally engaged as hereinafter set forth.

The release member 54 also includes an annular enlargement 66 integral with the tubular upper portion 56 and disposed within the casing 12, the enlargement 66 including a depending skirt portion 68 of somewhat reduced diameter, and a counterbore 70 which is substantially larger in diameter than the bore 58 through the tubular upper portion 56. The skirt 68 is provided with a relatively wide axial opening 72, and the enlargement 66 is provided with a narrower axial slot 74, thus to provide a shoulder 76 on the enlargement 66, the shoulder 76 being positioned adjacent to axial slot 74.

In the unactuated or break position of the breaker, the upper end portion of the bimetal thermoelement 44 is axially disposed within the skirt 68, with the thrust finger 52 extending outwardly through the opening 72 in the skirt, this position of the partsbeing best illustrated in Figs. 3 and 5. It will be seen that in this unactuated position of the circuit breaker, the annular enlargement 66 of the release member 54 does not exert latching shoulder 64. device, the shoulder 76 on release member 54 engages ,any downwardpressure on the thrust finger. 52 of the thermoeleme nt, so that the contact separating spring 42 .,1s permitted to hold the contacts in the open' position.

However, in the actuated or make position of the cir- 'cuit breaker, the release member 54 will be spaced downwardly a substantial distance from the upper plug 16 as best shown in Figs. 2 and 4, with thrust finger 52 engaged against shoulder 76 on the annular enlargement 66. so that the thermoelement 44 holds the contacts together against the force of contact separating spring 42.

It will be noted that the upper limit of travel of release member 54 in casing 12 is determined by engagement of the upwardly directed face 77 on annular enlargement 66 against the downwardly directed face 78 of the upper end plug 16.

An axially disposed aligning pin 79 is mounted in upper end plug 16, as by threaded engagement therein, and

' extends downwardly through an axial opening 80 in the Y enlargement 66 of release member 54, thus-to prevent any rotation of release member 54 in the casing, while permitting release member 54 to slide axially within the casing.

Release member 54 is preferably composed of insulat- "ing material.

A manual control cam bar 82 is slidable axially within the bore 58 of release member 54, and threadedly supports a plunger 84 at its upper end. The plunger 84 is reciprocable in an upwardly extending sleeve 86 formed on the upper end plug 16. Plunger 84 is provided with an internal recess 88 within which the upper end of latch release spring 90 seats. Spring 90 comprises a coil compression spring, with its lower end seating against an upwardly directed annular shoulder of the upper end of release member 54 by means of a pivot pin 100 so that the latch member 98 moves up and down reciprocably with the release member 54. Relative axial movement between cam bar 82 and the tube 56 is permitted, despite the presence of pivot pin 100, by means of an axial pin slot 102 in cam bar 82.

A cam pin 104 is mounted in cam bar 82 so as to extend across the axial slot 96, cam pin 104 being engaged through a cam slot 106 in the latch member 98. Cam slot 106 is offset at an acute angle relative to the axis of cam bar 82 so that downward movement of cam bar 82 relative to tube 56 will swing latch member 98 outward- 1y through axial slot 94 to a position in which the latch member 98 is engageable against the shoulder provided by flange 62 in the upper end plug 16, as shown in Fig.

4, whereas upward movement of the bar 82 within tube 56 will swing latch member 98 inwardly to the position as shown in Fig. 5. It will thus be seen that the latch member 98 functions as a cam follower that is controlled by the cam pin 104.

In order to actuate the circuit breaker from the unactuated position as shown in Figs. 3, 5 and 6 to the actuated position as shown in Figs. 2 and 4, all that is necessary is to manually push the plunger 84 downwardly or inwardly relative to the casing, moving cam bar 82 and release member 54 downwardly, downward force being applied to the tubular upper portion 56 of release member 54 through cam pin 104 and latch member 98. The plunger 84 thus moves downwardly until latch member 98 is forced radially outwardly under the end plug flange 62 so as to be frictionally engaged against the In this actuated position of the a rees thrust finger 52 of, the thermoelement, forcing the therrn6= element and the movable contacts downwardly against the force of contact separating spring 42 so as to cause engagement of the contacts. The force of contact separating spring 42 as transmitted through the thermoelement and through release member 54 and pivot pin 100 to latch member 98 provides the frictional engaging force of latch member 98 against the latching shoulder 64 so as to retain the device in the latched position.

-If it is desired to manually disengage the circuit breaker, all that is necessary is to pull upwardly on plunger 84, thus causing cam pin 104 to move upwardly relative to latch member 98 so as to cam the latch member ofi of the latching shoulder 64, thus to release the circuit breaker.

The circuit breaker will be automatically disengaged when an overload current passes through thermoelement 44 so as to mechanically shift the thermoelement thrust finger 52 off of shoulder 76 on the release member 54. When the thrust finger 52 moves olf of shoulder 76, the compressive force of contact separating spring 42 is instantaneously removed from the thermoelement 44 and hence from the release member 54, whereby the upwardly directed force of latch release spring on plunger 84 and on the cam bar 82 will cause cam pin 104 to swing the latch member 98 olf of the latching shoulder 64, whereby the latch release spring 90 is permitted to move the cam bar 82 upwardly, the bottom of axial pin slot 102 in cam bar 82 engaging the pin to move release member 54 to its uppermost position.

It will be apparent that if an attempt is made to actuate the circuit breaker while the condition of overload persists, when the contacts are made the bimetal thermoelement thrust finger 52 will immediately shift to a position off of the shoulder 76, whereby engagement is prevented, thus making the unit trip free. However, if the current is within the allowable range when the attempt is made to re-close the circuit breaker, the thrust finger 52 will again engage against shoulder 76 to per mit the latching mechanism to be engaged.

It will be noted in Fig. 4 that the cam bar 82 is provided with a downwardly extending portion 107 which extends inside of the thermoelement 44 when the circuit breaker. is in the actuated position. By providing cam bar 82 of aluminum or other non-magnetic metal, eddy currents will be induced in this extension 107 of the cam bar by surge currents through the thermoelement upon breaking of the contacts, thereby to apply a substantial upwardly pulling force to the cam bar 82 which assists the upward force of latch release spring 90. It will be appreciated that if the coil thermoelement was sufiiciently long, the cam bar 82 could extend substantially entirely through the coiled thermoelement, and could be provided with a tip of magnetic material which would be drawn upwardly toward the center of the thermoelement by surge currents through the thermoelement.

Referring now to the alternative embodiment 108 illustrated in Fig. 9, this embodiment is particularly adapted for heavy duty use, and includes ambient temperature compensating means. The alternative embodiment 108 includes a generally fiat, rectangular casing 110 that is preferably composed of a pair of complementary case sections 112 which are joined together so as to house the various working parts.

The casing 110 includes a closed bottom wall 116, generally flat side walls 118, edge walls 120, and a top wall 122 having a rectangular opening 124 therethrough. Mounted on the bottom wall 116 is a pair of widely spaced fixed contact members 18a having external conductors 20a connected therethrough. A pair of movable contact members 26a are supported in operative position gee-ease 'i'vetally mounted on insulating reak r bar 30a by means of respective pivot pins 32a, this pivotal supportmg of the movable'contact members causing a wiping action between the movable and fixed contacts as the cont acts are engaged and disengaged, so as to provide a self-cleaning action. p the preferred embodiment of the invention shown in Figs.

A similar wiping action occurs in 1-8, inclusive. I I r The casing is provided with a guide rib 128 which is engaged in a suitable slot in breaker bar 30a so as to provide axial direction to the sliding movement of breaker bar 30a.

A guide wall 130 extends upwardly from the closed bottom wall '116, and includes two semi-annular sections divided by opposed, axial guide slots 132 through :which radially inwardly directed fingers 33a of respective contact support arms 28a extend. Contact separating spring 49a, comprising'a coil compression spring, seats Within downwardly extending annular recess 134 in the bottom wall of the housing, the upper end of spring 40a V The bimetal thermoelement 44a is of helical construetion, and has its lower end attached to breaker bar 3911 by pin 460, the lower end of thermoelement 44a 7 being electrically connected to one of the contact support arms 28a by means of flexible conductor or pigtail" 48a, while the upper end of thermoelement 44a 'is similarly connected to the other contact support arm 2801 by flexible conductor pigtail Sea.

The latching mechanism and release means for the thermoelement are similar in construction to those of the preferred embodiment shown in Figs. 1-8, inclusive, or'

they may be like those shown in more detail in the second alternative embodiment of Figs. -13, inclusive, if desired. However, the latching mechanism of the embodiment shown in Fig. 9 is pivotally supported in the casing so as to be pivotally adjustable by the ambient temperature compensating means hereinafter described, in order to adjust the relative positioning between the latching mechanism and the thermoelement so as to provide adjustment of the sensitviity of the breaker. Accordingly, the latching and thermoelement release mechanisms are supported in the casing by providing a tubular support member 134 which corresponds to the upper end plug 16 of the preferred embodiment of Figs. 1-8, inclusive, but which is rotatably mounted in the casing.

The tubular support member 134 has a radially outward ly extending annular flange 136 thereon, flange 136 being positioned between a pair of support brackets 138 and a cover plate 140, the brackets 138 and cover plate 140 being held in position against the top wall 122 of -the casing by screws 144 or by other suitable means.

Release member 54a includes upwardly extending tubular portion 56a that is slidable in tubular support member 134, and also includes annular enlargement 66a and depending skirt 68a. The breaker is operated by manually controlling the actuation plunger 84a.

The ambient temperature compensating means pro- I vided in the embodiment of Fig. 9 is mechanically coupled to aligning pin 7901 so as to move pin 79a through an are, thus to rotate the release member 54a and tubular support member 134 in the casing. The aligning pin 792: extends downwardly from tubular support member 134 through an axial opening 80a in the annular enlargement 66a, the lower end of aligning pin 7911 being exposed for connection to the ambient temperature 'oom p'ensator.

An ambient temperature sensing chamber 1'46 is provided "in one 'of -the edge walls of the casing, and is exposed to the outside of the device through opening 148. 'A'therm'oelement is mounted in an opening 151 in the edgewall 120 inwardly of the'sensing'chamher 146, thermoelement 150 having a head portion 152 "mountedin the sensing chamber 146, and also having anexpanding and contracting bellows portion 154 inside "or the casing. The thermoelement 150 illustrated is of the type which contains solid liquid of a type which will give the desired expansion and contraction characteristics.

The inner end of bellows 154 is mechanically con 'n'ected to aligning pin 79a by means of a coupling arm Expansion of the bellows 154 upon an increase in ambient temperature will tend to further engage the upper end of the bimetal thermoelement unto the opposing shoulder of the annular enlargement 66a, so as to require a corresponding further increase in the temperatureof the thermoelement to release the breaker. Conversely, contraction 'of the bellows 1S4 upon a temperature'decrease will rotate the release member 54a in a direction so as to require less temperature of the thermoelement to move the thermoelement off of its opposed shoulder'on the annular enlargement 66a.

Referring now to the second alternative embodiment 158 of the inventionshown in Figs. 10, ll, 12 and 13,

this'embodiment is similar in construction to the embodiment of Fig. 9, but employs an ambient temperature compensating mechanism which utilizes a bimetal eleently preferred.

The casing or housing 160, the switching as'sembly, the thermoelement release assembly, and the latching assembly of the embodiment of Figs. "10-13 are all of the same construction as in Fig. 9, except that small support brackets 162 are employed in place of the support brackets 138 for supporting the tubular support member 1'34-in the housing, and the casing or housing -is slightly modified to accommodate the bimetal type of ambient temperature compensator.

It will be noted in Fig. 10 that the axial opening 80a through the annular enlargement 66a of the release member 54a comprises a groove opening at the periphery of enlargement 66a, and that aligning pin 79a is retained in this groove by means of a sleeve '164 engaged over the enlargement 66a.

7 nected near its other end to the outer end 168 of a coiled bimetal thermoelement 170. The coupling arm 166 has -a groove 172 therein which is received in a slot 174 in-theouter end 168 of thermoelement to provide this connection.

The inner end of the bimetal thermoelement 170 is integrally connected to a shaft 176 which is suitably journaled in housing 160. Shaft 176 is normally held against pivotal movement, so as to fixedly position the inner end of the coiled thermoelement .170, by means of an ear 178 integrally connected to shaft 176, and an adjusting screw 180 threadedly engaged in ear 178, screw 180 having a head portion 182 that is seated in a groove 184 in housing 160. Since the housing 160 is preferably composed of two complementary portions, the groove 184 may be provided in two mating portions in the opposing housing sections. The screw head 182 is exposed to the outside of the housing through a suitable aperture 12(6), which may be plugged after adjustment of the screw It will be apparent that rotation of screw 1'80 in one direction will rotate shaft 176, and hence theinner end of thermoelement 170, so as to urge the coupling 'arm 166 and aligning pin 79a in a direction to require more current "through the primary thermoelement 44a -of -the bar 82a, as by threaded engagement.

and cam bar 82a are urged toward an uppermost position by means of latch release spring 90:: which is engaged at its lower end against a shoulder 92a on the tu- 82a. 1 bar is disposed within the bore 58a in this embodiment.

breaker to release the breaker, while rotation of screw 180 in the opposite direction will permit release of the breaker upon the passage of less current through the primary'thermoelement 44a. Thus, it will be seen that the adjusting screw 180 actually provides means for adiusting the over-all sensitivity of the circuit breaker. It IS preferred to plug the aperture 186 when the sensitivity has thus been adjusted for any particular purpose.

In any set position of adjusting screw 180, the ambient temperature compensating thermoelement 170 will functron in a manner similar to the bellows type thermoelement 150 of Fig. 9 to compensate for ambient temperature variations.

Referring now particularly to Fig. ll, a modified form of the latching assembly is there shown, this modified latching assembly being particularly adapted for use in connection with the circuit breakers of Figs. 9 and 10 I wherein the ambient temperature compensating means I it compresses the primary thermoelement 44a downwardly so as to engage the contacts, comprises annular enlargement 66a, and tubular upper portion 56a, this upa per portion having internal bore 58a.

Plunger 84a is axially slidable in the tubular support member 134, and is attached to the upper end of cam The plunger 84a bular support member 134, and which engages at its upper end against a shoulder 188 of the plunger 84a.

Cam bar 82a is provided with an axial slot 96a which extends down through the lower end 192 of cam bar It will be noted that the lower end 192 of the cam A pair of overlapping latch members 194 are positioned in axial slot 96a, and are pivoted at their upper ends by means of pin 196 in bar 82a. Latch members 194 are provided with radially outwardly extending ears 198, the ears having upwardly facing latching shoulders 200, downwardly facing inclined cam follower surfaces 202, and transverse locking surfaces 204 at the inner ends of the inclined cam follower surfaces 202.

Fixedly positioned in the lower end of bore 58a is a cam member 206, held in position by a pin 208, this cam member including a flat, upwardly facing surface 210 and a bevelled upper edge portion forming an inclined cam surface 212.

v -Disposed directly under the flange 62a within tubular support member 134 is an anti-friction washer 21'4, 'comt posed of Teflon or other suitable material, below which is positioned a metallic latch washer 216, these washers I being held in position by a snap ring 218 disposed in a suitable groove 220 within support member 134.

The operation of this alternative latch mechanism shown in Fig. 11 is generally the same as the latch mechanism shown in connection with Figs. 1-8, inclusive. However, when the breaker is in the actuated or make position, the latch members 194 are more positively locked vin the latching position by the axial compression of the parts. In the latching position, as illustrated in Fig. 11, the latch members 194 are both swung outwardly so that their transverse locking surfaces 204 are engaged, under pressure, by the upwardly facing flat surface 210 on cam member 206, thereby to lock the latch members 194 in the latching position. In this position, the'ears 198 of the latch members extend radially outwardly through axial slots 222 in tube 56a so that the upwardly facing latching shoulders 200 engage against the latch washer- 216.

When the primary thermoelement 44a shifts sufiiciently under overload current conditions to release the pressure of the cam member against the latch members, the latch release spring 90a will take over to move cam bar 82a upwardly through tube 56a, thus to swing the latch members 194 inwardly out of the way of the latch washer 216. When it is again desired to engage the breaker, the plunger 84a is moved downwardly to shift cam bar 82a downwardly in tube 56a, causing latch members 194 to move downwardly relative to cam member 206, whereby the inclined cam follower surfaces 202 on the latch members will engage against the inclined cam surface 212 of cam member 206 to cam the latch members outwardly to the latching position as shown in Fig. 11.

While the instant invention has been shown and described herein, in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A circuit breaker which comprises: a housing; a pair of spaced, fixed contacts mounted in the housing; a breaker bar composed of insulating material movably mounted in the housing; a pair of spaced, movable contacts mounted on said breaker bar, said breaker bar being movable between an open circuit position in which said movable contacts are spaced from said fixed contacts and a closed circuit position in which said movable contacts engage the respective said fixed contacts; first spring means biasing said breaker bar and movable contacts toward said open circuit position; a bimetal thermoelement having means thereon engageable with said breaker bar and having shoulder means thereon; an electrical connection between one of said movable contacts and a first point on said thermoelement, and an electrical connection between the other said movable contact and a second point on said thermoelement; release means having a shoulder thereon movably mounted in said housing, said release means being movable between an open circuit position in which said shoulder is spaced from said shoulder means on said thermoelement so as to permit said breaker bar and movable contacts to be held in their said open circuit positions by said first spring means, and a closed circuit position in which said shoulder is compressed against said shoulder means on the thermoelement so as to hold said breaker bar and movable contacts in their said closed circuit positions; a latching surface in said housing; a latch member movably mounted on said release means so as to move between a release position in which it clears said latching surface to permit said breaker bar and movable contacts to be moved by said first spring means to their open circuit position, and a latched positions in which the latch member is held in latching engagement with said latching surface by the compressive force of said first spring means; second spring means biasing said latch toward its said release position; and means on said release means for moving said release means to its said closed circuit position and for moving said latch member to its said latched position; thermo-mechanical shifting of said thermoelement upon the passage of an overload current therethrough causing said shoulder means on the thermoelement to move off of said shoulder so as to release the able contacts to their said open circuit position.

2. A circuit breaker as defined in claim 1 wherein said first spring means comprises a coil compression spring, one end of which engages against the housing; and a apeaeao "shuntmember'engaged by the other end'ofsaid coil com- -pressionspring, said shunt member being held against said movable contacts by the biasing force 'of said coil being engaged against said support arms on the other side of the pivot.

44A circuit breaker as defined in claim 1 wherein said breaker bar and release means are coaxially slidable, and wherein. said thermoelement comprises a helically coiled bimetal strip, said first end of the thermoelement being disposed proximate said movable-contacts,

whereby surge currents through the coiledthermoelemerit upon disengagement of the breaker contacts will cause magnetic blow-out of aiming across theopening "contacts.

5. A circuit breaker as defined in'claim 4-wherein said housing is cylindrical, said fixed contacts being positioned in one end of the housing, and said-breaker bar,

coiled thermoelement and release meansbeing axially aligned in the tubular housing, wherebyrapidly expanding gases resulting from arcing upon disengagement of "the breaker contacts will flow axially in the housing "away from .the fixed contacts at one 'end' of the housing, causing gas blowout of arcing across the opening con- "tacts.

6. A circuit breaker as defined in claim 4-wherein a metallic extension of said release means extends within said coiled thermoelement from said second end of said thermoelement so that surge currents through the thermo- I shift said release means in the-housing upon variations in ambient temperature, thereby adjusting said shoulder on the release means with respect to said shoulder means on the thermoelement to compensate for the efiect of ambient temperature changes on the thermoelement.

8. A circuit breaker as defined in claim 7 wherein'said ambient temperature compensating thermoelement is a bimetal strip.

9. A circuit breaker as defined in claim 7 wherein-said ambient temperature compensating thermoelement is a temperature responsive bellows.

10. A circuit breaker as defined in claim 7 wherein said ambient temperature compensating thermoelement is adjustably positioned in the housing, and adjusting means connected to the ambient temperature compensating thermoelement and to the housing for adjusting the position of the temperature compensating thermoelement so as to adjust the sensitivity of the circuit breaker.

'11. A circuit breaker'as defined in claim 7 wherein said first spring means comprises 'a coil compression spring, one end of which engages against the housing; and a shunt member engaged by the other'end of said coil compression spring, said shunt member being held against said movable contacts by the biasing'force of said coil compression spring.

12. A circuit breaker which comprises: a-hous'ing, .a

"pair of spaced, fixed contacts mounted inthe housing;

a breaker bar composed of insulating material slidably mounted in the housing; a pair of spaced, movable con *tactsmounted on said breaker bar, said breaker bar be- 'in'g slidable between "an open circuit position in which said movable contacts arespaced 'fromsaidfixed contacts and-a'closedcircuit position in which said movable contacts engage the respective said fixed contacts; a first coil compression spring biasing said breaker bar and movable contacts toward said open circuit position; a bimetal thermoelement comprising a helically coiled bimetal strip, said thermoelement having means thereon engageable with said breaker bar and having shoulder means thereon; an electrical connection between one of said movable contacts and a first point on said thermoelement, and an electrical connection between the other movable contact and a second point on said thermoelement; release means slidably mounted in the housing so as to slide coaxially with respect to said breaker bar, said release means including a release member having a shoulderthereon and being slidable between anopen circuit positionin which said shoulder is spaced from said shoulder means'on said thermoelement so as to permit the breaker bar and movable contacts to be held in their said opencircuit positions by saidfirst spring, and a closed circuit position in which said shoulder is compressed against said shoulder means on the thermoelement so as to hold the breaker bar and movable contacts in their saidclosed circuit positions, said release member including-an integral tube member; a plunger extending outside of the housing; a cam bar member connected to the plunger and extending into said tube member portion of the releasemember so as to be axially slidable in said tube; a second coil compression spring mounted in the housing so as to bias the plunger and cam bar in a direction axially away from the fixed contacts; a latching surface in the housing; a latch member pivotally mounted on one of said tube and cam bar members so as to pivot between a release position in which it clears said latching surface to permit'said breaker bar and movable contacts to be moved by said first coil spring to their open circuit positions, and a latched position in which the latch memberis held in latching. engagement with said latching surface by the compressive force of said first coil spring; and cam means engageable between the other'one of said tube andcam bar members and said latch member when'said cam bar is moved inwardly of said tube so as to cause latching of the latch member on said housing surface; thermomechanical shifting of said thermoelement upon the passage of an overload current therethrough causing-said shoulder means on the thermoelement to move otf of said shoulder so as to release the compressive force holding the latch member in its latched position, whereby to release the circuit breaker.

13. A circuit breaker as defined in claim '12 wherein said latch member is pivotally mounted on said tube member, and said cam means includes a transverse cam pin on the cam bar member and engaged through a cam slot in said latch member.

14. A circuit breaker as defined in claim 12 wherein said latch member is pivotally mounted on said cam bar member, and said cam means includes a cam member in the tube member and a cam face on the latch member.

15. A circuit breaker as defined in claim 14 wherein a radially oriented face on the cam member engages a radially oriented face on the latch member in the latched position of the latch member, to hold the latch member in its said latched position when compression is applied between the latch and cam members.

References Cited in the file of this patent UNITED STATES PATENTS 2,289,305 Hitchcock July 7, '1942 2,326,529 Frese Aug. 10, 1943 2,409,917 Von Hoorn Oct. 22, 1946 2,464,943 Rockwood Mar. '22, 1949 2,831,086 Ingwersen et al Apr. 15, '1958 2,838,635 Ingwersen June 10, 1958 2,912,546 Arey Nov. 10, .1959 

